Medical drugs and solvents are often supplied in glass or plastic containers, such as vials, bottles or bags, which are sealed by a rubber, plastic or elastomeric bung, stopper, membrane or puncturable cap. Such sealing members prevent deterioration or contamination of the drug, allow the contents of a container to be mixed by shaking, and prevent the contents of the container from leaking out and contaminating the surroundings. A cannula or a hollow spike comprising a flow channel and an opening that communicates with the flow channel, is usually inserted through such a sealing member to supply fluids to the container and to withdraw fluid therefrom.
If an infusion fluid container is made of a rigid or semi-rigid material, i.e. if its walls are non-collapsible, an air inlet is required to withdraw medical fluid from the infusion fluid container and prevent the formation of a vacuum therein. When withdrawing fluid from a rigid or semi-rigid infusion fluid container, a spike having a medical fluid flow channel and an air inlet passage, usually comprising an air filter, is therefore used.
When a container comprising medical fluid is nearly empty a cannula or spike is often used to withdraw the last few drops of the medical fluid (which may be very expensive and/or toxic) from the container to minimize waste and to facilitate cleaning/disposal of the container. The cannula or spike is slowly and carefully retracted through the sealing member while withdrawing the medical fluid remaining in the container. However, a toxic drug may leak out and contaminate the surroundings during such a procedure and non-filtered air containing undesirable particles such as dust, pollen or bacteria may be drawn into the cannula and thus contaminate the medical fluid therein.
In some cases containers are in fact provided with an extra amount of the drug that is to be withdrawn to allow for the fact that not all of the drug will be withdrawn from the container. A user is then able to withdraw the recommended number of doses from the container but doing so will increase the cost of each container of medical fluid, increase waste and make cleaning or disposal of the container more complex.
Since sealing members are available in a wide variety of configurations, sizes and thicknesses, it is difficult to design a spike that is suitable for use with a plurality of different sealing members and which makes it possible to withdraw the last few drops of a medical fluid out of the containers in a safe and convenient way.